1. Field of the Invention
The present invention relates to a connecting rod assembly used in association with an engine and also to a bearing-equipped connecting rod.
2. Description of the Prior Art
The connecting rod is generally manufactured by forging or sintering a steel rod or a plate member or by means of a constrained compressive molding. Also, the connecting rod is often prepared from a steel plate by the use of a press work.
Where the connecting rod is manufactured by the use of a forging or sintering technique, the number of process steps is generally large, hampering reduction in cost of manufacture. Also, when it comes to boring to be performed on the connecting rod, grinding is necessitated and, therefore, the number of process steps increases correspondingly.
In the case of the connecting rod formed by the use of a standard blanking technique, by the influences brought about by a cut plane 32a formed on an inner peripheral surface 32 of one or both of big and small end portions 30 and 31 as shown in FIG. 7, a bearing member 33 tends to tilt when the bearing member 33 is press-fitted into the inner peripheral surface 32. Because of this, the post processing such as grinding or polishing is required, resulting in increase of the cost of manufacture.
To alleviate the above discussed problem, a connecting rod has been suggested in the Japanese Patent Application No. 2001-133940, which is formed by the use of a blanking technique with a fine blanking press. With the fine blanking press, the proportion of the cut plane in the inner peripheral surface and the proportion of a shear plane in the same inner peripheral surface can be reduced and increased, respectively, and, therefore, as compared with the use of the standard blanking technique with the standard press, the possible tilt of the bearing member tending to occur during the press fitting can be reduced. However, since the fine blanking press is a special tool, the use thereof tends to result in increase of the manufacturing cost. Also, even with the fine blanking press, influences brought about by the cut plane are so inevitable that as exaggeratedly shown in FIG. 8, the inner peripheral surface 32 in one or both of the big and small end portions 30 and 31 tends to be tapered. For this reason, when the bearing member 33 is press-fitted in the inner peripheral surface 32, the bearing member 33 tilts to some degree.